Hack saw



E. M. LANG.

HACK SAW.

APPLICATION FILED SEPT-15,1919. RENEWED MAR. 30. 1922.

1L 4;S% 25 Patented 0% 31, 1922,

l 4.1 9- 1. MAMAMA/VMA/M/MAAMAMMAMAMMAMAWAAMAAWM WAJ l atented (left. 31, 1922.

warren stares PATENT cannon.

EDWARD IVE. LANG, OF PORTLAND, MAINE.

CK SAW.

Application filed September 15, 1919. Serial No. 323,922. Renewed March 30, 1922. Serial No. 548,189.

To all whom it may concern:

Be .it known that I, EDWARD M. LANG, a citizen of the United States, residing at Portland, in the county of Cumberland and State of Maine, have invented certain new and useful Improvements in Hack Saws, of which the following is a specification.

My invention relates to saw blades for sawing metal commonly known as hack saws.

Under old conditions, when steel was comparatively cheap, hack saws were made with a line of teeth on one edge only and when the teeth were Worn out the saw was thrown away or discarded.

These saws are necessarily hardened throughout so as to give theteeth the utmost wearing qualit but as a result of'this hardening process t e saws become brittle and are easily broken.

The object of my invention is to prolong the life of the saw and also to make it stronger and less liable'to breakage.

I accomplish this object by! forming. the teeth on both edges of the hack saw blade and by concaving the same in cross section so that the two edges of the blade will be thicker than the center. v

The teeth are preferably formed without set, or they may be set in the usual manner.

These hack saw blades are usually broken by becoming bound or cramped in the saw scarf. It is desirable, therefore, that the body of the saw in rear of the teeth shall have as much clearance as possible so that it will be less liable to bind or cramp in the saw scarf than when the blade is perfectly uniform in thickness as under the old practice.

moment and twist as the thickened edge'hasa tendency to resist these strains. The central or neutral. line of the blade is subjected to far less strain than the edges so thatthe metal can be spared from that point and disposed along the edges with the advantage of making a much stronger blade.

. part of the out before the scarf has become sufficiently deep to form a guide for the saw.

By forming the saw according to my inventlon, the sides of the blade recede rapidly from the edges of the teeth and the blade is less liable than in the old form to cramp against the edges of the saw scarf.

. In constructing a hack saw blade in accordance with my invention, I am able to make the two lines of teeth of different pitch thus adapting the saw to several kinds of work. I practicall double the wearing life of the blade by dou ling the number of teeth and construct a blade of far greater strength than if the same was formed in the aid manner.

' The invention is particularlyvaluable in the case of power hack saws which are of considerable width and in which the breakin% strains are often very great.

he teeth of the saw if without set are stronger and heavier than when made with a set, being less liable to break since the metal has not been laterally bent or set.

I have illustrated my invention in the accompanying drawing in which:

gig. 1 is a slde elevation of the saw blade an a Fig. 2 is an enlarged cross section.

Referring to the drawing, 1 represents the body of the blade and 2 the teeth, a line of which is formed on each edgeof the blade.

The blade is concaved in cross section from edge to edge, the concavity extending preferably to the outer edges of the teeth so that the outer edges of the teeth are slightly wider than their bases. The teeth, as here shown, are not set or bent laterally so that the are not weakened in the act of setting.

he outer edges of the teeth being slightly wider than the body of the saw back of the base a saw scarf Will be produced Wider a concave cross section and thickened edge.

than the body! of the saw and so will prevent I claim: 10 thebinding and cramping of the saw. A hack saw blade having teeth on both The hack saw blade thus produced is edges and having a concave cross secti0n.*-

5 strong and contains double the wearing stir- In testimony whereof I have aflixed my face of the ordinary hack saw blade. It can signature. be made as cheaply as the ordinary hack r saw by having the steel specially rolled with EDWARD M. LANG. 

